Logical which uses fields from two or more physical files.
CAT – Concatenate two variables or constants into one continuous string. BCAT – Truncates all trailing blanks in the first character string, one blank is inserted, then the two character strings are concatenated. TCAT – Truncates all trailing blanks in the first character string, the two character strings are concatenated.
Dynamic select occurs whenever the program reads file. But access path occurs before the file is read (but not necessarily). Because access path maintenance performed on the file.
This is used to specify rules for the Selection/Omission of records from a Physical File.